1. Field of the Invention
This invention relates to a hydraulic cement composition for dental use, and in particular to a cement composition having good compression strength and workability. The composition is suitable for producing dental fillings, inlays, or crowns. The quantity of water required for kneading will vary depending on the use of the respective proposes.
2. Description of the Prior Art
In the past, zinc phosphate-based cements predominated in dental use. However, it can be seen from West German Patent Laid Open No. 1617688 that rapid development of polycarboxylate cements has taken place in recent times. The advantage of polycarboxylate cement is that it is less of a stimulant to dental pulpa and adheres better to dentine compared to zinc phosphate cement. Nevertheless, it has the disadvantage that its compression strength is lower by about 400-500 kg/cm.sup.2 than that of zinc phosphate cement which has a compression strength of about 1200-1300 kg/cm.sup.2. In addition, polycarboxylate cement used heretofore was usually employed as a 50% aqueous solution in polyarylic acid (viscosity: 5000 cps), with the result that the viscosity of its kneading solution was considerably higher than that of zinc phosphate cement. This caused difficulty in kneading and also caused reduction in both compression strength and adhesion because of the inclusion of air bubbles in the course of kneading or molding.
A need, therefore, continues to exist for a polycarboxylate cement composition having high compression strength.